1. Field of the Invention
The present invention relates to the treatment of bacteria contaminated wells, and more particularly, to methods of treating previously fractured bacteria contaminated subterranean formations to substantially reduce or eliminate such contamination.
2. Description of the Prior Art
The presence of anaerobic bacteria in an oil and/or gas producing formation, and particularly sulfate reducing bacteria (SRB), cause a variety of problems. If the bacteria produce sludge or slime, they can cause a reduction in the porosity of the formation which in turn reduces the production of oil and/or gas therefrom. Sulfate reducing bacteria produce hydrogen sulfide, and the problems associated with hydrogen sulfide production, even in small quantities, are well known. The presence of hydrogen sulfide in produced oil and gas can cause excessive corrosion in metal tubular goods and surface equipment, a lower oil selling price, and the necessity to remove hydrogen sulfide from gas prior to sale.
When the fluids utilized in drilling or stimulating oil or gas wells contain bacteria, the producing formations can become contaminated with the bacteria. Such contaminated formations which have been fractured have heretofore been particularly difficult or impossible to treat. That is, prior attempts to introduce one or more bactericides into such formations to contact and kill the bacteria therein have been largely unsuccessful due to the bacteria being located in or near fractures at long distances from the well bores. When treating fluids containing bactericides have been pumped into such previously fractured contaminated formations, the treating fluids have either failed to reach the locations of the bacteria, and/or the proppant materials in the previously formed fractures have been disturbed thereby reducing the productivities of the formations.
By the present invention, improved methods of treating previously fractured bacteria contaminated subterranean formations are provided whereby the bacteria are substantially eliminated without lowering the productivities of the formations.